This invention relates to a thermoplastic bag useful for storage of isolated materials including living cells such as blood platelets, and a method for long-term storage and utilization of such living cells including the introduction of same in the bag, insitu freezing and storage at cryogenic temperatures, and thawing and discharge from the bag when needed.
Living cells such as blood platelets are presently stored in the frozen form in single layer bags fabricated from a flexible plastic material as for example polyethylene. The bags are fitted with tubular inserts as access openings which are heat-sealed in position as ports. Heat seals are applied to the top and bottom of the bags to effect bag closure. This commercially employed bag is sterilized by ethylene oxide which unfortunately renders it unsuitable for use as a container for the cryoprotectant solutions into which the cells must be placed prior to low temperature processing. This limitation requires the blood banker to procure his own solutions and transfer the volume needed to the bag. Accordingly, it is not possible to provide a sterilized cryoprotectant-filled bag which would be useful as a blood bag under standardized procedures for handling.
Other disadvantage of the aforedescribed blood storage bag formed from a single layer of plastic film is that the same tends to be fragile at cryogenic temperatures. This is inherent in any single layer material. Whereas breakage of a bag containing whole blood or red blood cells may be a tolerable economic loss (assuming replacement blood of the same type is available), such breakage and product loss is unacceptable in the case of valuable living cell material more difficult to obtain and process such as blood platelets.
Another disadvantage of prior art living cell storage bags is that they require additional manufacturing steps to add tubular inserts through access openings, and thereafter heat seal the inserts in position as ports. These are time consuming and expensive steps, and the resulting product is three dimensional in shape even when empty, hence inconvenient for storage.
An object of this invention is to provide an improved bag useful for storage of isolated materials. Another object of this invention is to provide an improved bag useful for storage of living cells which is heat sterilizable, structurally stable at temperature as low as -196.degree. C. and also at elevated temperature suitable for sterilization such as above 127.degree. C.
Another object is to provide an improved bag which does not require separate tubular inserts for access ports, and which is flat and two dimensional prior to filling.
Still another object is to provide a package comprising a thermoplastic bag containing cryoprotectant solution which can be heat sterilized insitu.
A further object of this invention is to provide an improved method for long-term storage of living cells by introduction in a thermoplastic bag, freezing and storage, thawing and discharge when needed.
Other objects and advantages of the invention will be apparent for the ensuing disclosure and appended claims.